The present invention relates generally to an apparatus for producing a yarn spun from a loose fibre array supplied to the apparatus. The invention relates more particularly to an arrangement in which a fibre array passes through a vortex chamber and is subject to a vortex flow of a fluid and are spun into a yarn.
Spinning devices of the type mentioned above are disclosed for example in U.S. Pat. Nos. 5,528,895 and 5,647,197 (both by Murata). These devices comprise a fibre supply duct and a yarn take-off duct. An outlet zone of the fibre supply duct is oriented essentially towards the inlet zone of the yarn take-off duct. An outlet opening of the fibre supply duct is arranged at a distance from the yarn take-off duct. A twist stop means (e.g. an eccentric edge over which the fibres are pulled, or a substantially concentric pin around which the fibres are guided) is provided in the zone of the outlet opening of the fibre supply duct.
The inlet zone of the yarn take-off duct is normally laid out as a slender spindle surrounded by an exhaust duct having an essentially annular cross-section. The exhaust duct extends from the intermediate mom laid out as a vortex chamber substantially parallel to the yarn take-off duct. The vortex chamber in this arrangement is of essentially the same diameter as the inlet zone of the exhaust duct and is provided with nozzles directed tangentially into the chamber for injecting a fluid (e.g. air). The fluid injected into the vortex chamber is sucked off through the exhaust duct. The vortex flow generated in the vortex chamber is taken around the yarn take-off duct (spindle) and into the exhaust duct. The vortex chamber and an inlet zone of the exhaust duct thus substantially form a functional unit that imparts twist. Also, the yarn take-off duct, which can be rotatable, also can assist the twist imparting action. Various means ensure that the fibres are pressed against the wall of the yarn take-off duct and are carried effectively.
The cross-sections of the fibre supply duct the yarn take off duct and the exhaust duct are small compared to the mean length of the processed fibres. The length of the fibre supply duct is laid out so that at least part of the fibres are held in the inlet zone of the fibre supply duct (e.g. between the delivery rolls of a drafting system arranged upstream from the fibre supply duct). The part of the fibres held are the leading ends which already have reached the zone of the yarn take-off duct.
Fibres supplied to an apparatus as described briefly above are held in the fibre array. From the outlet opening of the fibre supply duct, these fibres are guided into the yarn take-off duct substantially without having twist imparted thereto. The fibres in the zone between the fibre supply duct and the yarn take-off duct are subject to the centrifugal influence of the vortex flow, and are radially driven away from the inlet opening of the yarn take-off duct. Yarns produced using the method described thus have a core of fibres extending essentially in the longitudinal direction of the yarn or fibre portions without substantial twist. An outer zone is also present in which the fibres or fibre portions are wrapped around the core.
This yarn structure has leading fibre ends that directly reach the yarn take-off duct in particular fibres having trailing ends are still held in the fibre supply duct. Trailing fibre ends under the influence of the vortex flow are pulled out of the fibre array and are wrapped around the yarn being formed. In particular, trailing fibre ends are no longer held in the inlet zone of the fibre supply duct. Also, leading fibre ends under the influence of the vortex flow are angled off from the fibre array while the trailing fibre end remains in the fibre array. This results in the formation of loops, which can be seen in the corresponding yarn.
Fibres are held in the generated yarn and are pulled into the yarn take-off duct. At the same time, the fibres are subject to the vortex flow that accelerates the fibres centrifugally, i.e., away from the inlet opening of the yarn take-off duct, thereby pulling the fibres towards the exhaust duct. The fibre portions pulled from the fibre array by the vortex flow form a fibre vortex that merges into the inlet opening of the yarn take-off duct. Longer portions are wrapped spirally about the outside of the spindle-shaped inlet zone of the yarn take-off duct. The portions in this spiral are pulled towards the inlet opening of the yarn take-off duct against the force of the flow in the exhaust duct. Fibres of which neither the leading end nor the trailing end are pulled into the yarn, are carried away through the exhaust duct, and thus represent undesirable fibre losses.
The spinning method described is characterized in that very high spinning speeds can be achieved (up to ten times higher than in ring spinning). On the other hand it is difficult to prevent high fibre losses using this method, and to achieve a sufficiently high proportion of fibres in the twisted outer zone of the yarn cross-section.
Various features and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned from practice of the invention.
The present invention proposes a change and an improvement to the apparatus, which uses the spinning method described above. The present invention thus provides for an apparatus for spinning using a vortex flow. The apparatus permits reduction of fibre losses compared to the state of the art, and maintains at least equal yarn quality.
The present invention is based on the idea that the vortex chamber and the exhaust duct are functionally separated in such a manner that the fibre vortex cannot extend indefinitely downstream into the exhaust duct. The fibre vortex remains limited to the vortex chamber, i.e. to a room functionally separated from the exhaust duct. In one exemplary embodiment the vortex chamber is limited by a wall, and the fluid is guided through this wall into the exhaust duct. The inlet opening of the yarn take-off duct may be arranged at the centre of the wall that forms a downstream limitation of the vortex chamber. The wall that forms the downstream limitation of the vortex chamber does not exert any twist imparting function, i.e. it does not rotate. For draining the fluid, openings are provided in this wall distributed around the yarn take-off duct merging into the one or a plurality of exhaust ducts. The openings can be united into an annular opening.
The functional separation of the vortex chamber and the exhaust duct reduces the probability of fibre losses via the exhaust duct. Fibres in the fibre vortex of which no ends are caught in the generated yarn remain longer in the vortex chamber. The probability that the fibres are carried on by the end portions of twirling fibres held in the yarn increases. This effect reduces undesirably high fibre losses, which occur according to the present state of the art.
In one exemplary embodiment of the present invention, the wall may be in the shape of an obtuse cone and formed on or as a part of a yarn take-off duct. Alternatively, in another exemplary embodiment of the present invention the wall may be a wall plate that has a plurality of openings disposed therethrough. The openings may extend in an inclined direction in the direction of vortex flow through the wall plate. Additional exemplary embodiments of the present invention exist where the wall is a wall plate that has a plurality of slot-shaped openings distributed along the circumference of the wall plate.
Various forms of the apparatus for producing a yarn spun from a loose fibre array using a vortex flow are disclosed. Exemplary embodiment in more detail with reference to the drawings are shown.